Method for generating a pulsed magnetic field and associated device

Abstract

The invention concerns a method for generating a pulsed magnetic field, the method being implemented using a device ( 10 ) comprising an electrical supply ( 20 ), a switch ( 25 ), a capacitor ( 15 ) and a coil ( 30 ) having a first extremity ( 80 ) connected to an electrical ground and a second extremity ( 85 ), the capacitor ( 15 ) comprising a first electrode connected to the electrical ground and a second electrode, the switch ( 25 ) being able to commute between a first configuration wherein the second electrode and the second extremity ( 85 ) are electrically insulated and at least one second configuration wherein the second electrode and the second extremity ( 85 ) are electrically connected, the capacitor ( 15 ), the switch ( 25 ) and the coil ( 30 ) forming a series circuit when the switch ( 25 ) is in the second configuration, the series circuit being underdamped.

The invention claimed is: 
     
       1. A method for generating a pulsed magnetic field, the method being implemented using a device comprising an electrical supply, a switch, a capacitor and a coil having a first extremity connected to an electrical ground and a second extremity, the capacitor comprising a first electrode connected to the electrical ground and a second electrode, the switch being able to commute between a first configuration wherein the second electrode and the second extremity are electrically insulated and at least one second configuration wherein the second electrode and the second extremity are electrically connected, the capacitor, the switch and the coil forming a series circuit when the switch is in the second configuration, the series circuit being underdamped, the method comprising:
 a first step for charging the second electrode with a first electrical charge having a first polarity, the switch having the first configuration, 
 a first step for discharging the first electrical charge through the coil to generate a first pulse of magnetic field, the switch having the second configuration, 
 a second step for charging the second electrode with a second electrical charge having a second polarity different from the first polarity, the switch having the first configuration, and 
 a second step for discharging the second electrical charge through the coil to generate a second pulse of magnetic field, the switch having a second configuration. 
 
     
     
       2. The method according to  claim 1 , wherein the first step for charging, the first step for discharging, the second step for charging and the second step for discharging are repeated with a repetition rate superior or equal to once per second. 
     
     
       3. The method according to  claim 1 , wherein a capacitance is defined for the capacitor, an inductance being defined for the coil, a resistance being defined for the series circuit, the capacitance, the inductance and the resistance being such that the following equation is verified: 
       
         
           
             
               
                 L 
                 R 
               
               ≥ 
               
                 C 
                 
                   
                     0 
                     . 
                     1 
                   
                   ⁢ 
                   6 
                 
               
             
           
         
         wherein L is the inductance, R is the resistance and C is the capacitance. 
       
     
     
       4. The method according to  claim 1 , wherein the switch comprises two arms connected in parallel between the second extremity and the second electrode, each arm comprising a thyristor and a diode connected in series, the diode and thyristor of each arm being each inverted with respect to the diode and thyristor of the other arm. 
     
     
       5. The method according to  claim 1 , wherein each first and second step for discharging is immediately followed by a temporization step, the switch being in the first configuration and the second electrode being electrically disconnected from the electrical supply during the temporization step, the temporization step having a time duration superior or equal to 5 milliseconds. 
     
     
       6. The method according to  claim 1 , wherein each step for discharging comprises successively:
 1. A first step for commuting the switch from the first configuration to a second configuration, 
 2. a step for discharging the second electrode through the coil, and 
 3. a second step for commuting the switch to the first configuration, 
 a time period between the first step for commuting and the second step for commuting being comprised between 10 microseconds and 100 microseconds. 
 
     
     
       7. The method according to  claim 1 , wherein each first or second step for charging comprises steps for:
 electrically connecting the second electrode to the electrical supply, 
 estimating a value of the electrical charge of the second electrode, and 
 disconnecting the second electrode from the electrical supply when the value of the electrical charge is equal to a predetermined value. 
 
     
     
       8. A computer program product comprising software instructions configured to implement a method according to  claim 1  when the software instructions are executed by a processor. 
     
     
       9. An information-carrying medium onto which a computer program product according to  claim 8  is memorized. 
     
     
       10. A device for generating a pulsed magnetic field comprising an electrical supply, a switch, a capacitor, a control module and a coil having a first extremity connected to an electrical ground and a second extremity, the capacitor comprising a first electrode connected to the electrical ground and a second electrode, the switch being able to commute between a first configuration wherein the second electrode and the second extremity are electrically insulated and at least one second configuration wherein the second electrode and the second extremity are electrically connected, the capacitor, the switch and the coil forming a series circuit when the switch is in the second configuration, the series circuit being underdamped,
 the electrical supply being able to commute being a third configuration wherein the electrical supply is able to charge the second electrode with an electrical charge having a first polarity and a fourth configuration wherein the electrical supply is able to charge the second electrode with an electrical charge having a second polarity different from the first polarity, 
 the control module being able to command the electrical supply to commute between the third configuration and the fourth configuration, the control module ( 35 ) further being able to command the supply ( 20 ) to connect to or disconnect from the second electrode ( 45 ), the control module ( 35 ) being configured to implement the steps of a method according to  claim 1 .